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The lattice parameters of various quartz types and occurrences. The asterisks in the Obs. column indicates measurements performed by the authors; R****** is the RRUFF database code for the quartz occurrences considered.
Source publication
The blue quartz of the Albești metagranite is an interesting and puzzling occurrence in the Romanian geological landscape, both in terms of rarity and available data. The body of literature on blue quartz attributes the color to the Rayleigh/Tyndall scattering of light by nanometer/submicron inclusions, commonly identified as ilmenite or rutile, an...
Context in source publication
Context 1
... powder diffractions performed on quartz grains from the Albești metagranite and Llano rhyolite showed no relevant differences between the two. Based on the diffraction data, the a and c lattice parameters of the two blue quartz occurrences were calculated and compared to other varieties available in the RRUFF database (Table 1). The comparison has shown that the lattice parameters of the various quartz occurrences can vary significantly, as a function of chemical impurities, lattice distortions, and even sample preparation, and that the two blue quartz occurrences considered are in no way outstanding with respect to the lattice constants. ...Similar publications
The distribution of ultrahigh-pressure metamorphism (UHP) at the scale of a mountain belt is of prime importance for deciphering its past subduction history. In the Western Alps, coesite has been recognized in the southern Dora-Maira Massif, in the lens-shaped Brossasco-Isasca Unit, but has not been found up to now in the other parts of the massif....
Citations
... The consensus is that blue quartz is usually hosted by plutonic and volcanic intermediary to acidic rocks (or their metamorphic equivalent) and that, when hosted by metamorphic rocks, the occurrences are related to amphibolite-granulite facies conditions, as summed up by Pantia & Filiuță (2019). The geological significance of these occurrences is largely undetermined (Zolensky et al., 1988;Seifert et al., 2011), although potential applications of metamorphic blue quartz in determining the metamorphic history of the area of occurrence have been suggested (Pantia & Filiuță, 2021). ...
... The CIPW normative composition places the Albești metagranite in the monzogranite field, in close proximity to the granodiorite (Robu & Robu, 1996). It is worth mentioning that not all Albești metagranite outcrops show blue quartz, and it is possible that the outcrops which experienced more intense metamorphic conditions lost the blue coloration in their rock forming quartz as it recrystallized (a metamorphic effect observed in other occurrences as well), as suggested by Pantia & Filiuță (2021). ...
... Inclusions mostly consist of biotite, but iron oxides, pyrite, and chalcopyrite were also identified under the electron microscope. When present, the biotite/iron oxide inclusions tend to concentrate in the colorless areas of the quartz grains (Pantia & Filiuță, 2021). The identity of the scattering particles responsible for the blue color is still unknown. ...
Rock forming blue quartz occurrences are reported on all continents, but little is known about the specific causes for the coloration, and even less about its geological significance. The present study investigates the occurrence hosted by the metarhyolites of the Rio dos Remédios Group in order to determine the potential causes of the blue coloration and gain insight into the geological significance of the occurrence in the wider context of Brazilian geology. The optical observations have shown that the blue color is likely the result of the Rayleigh scattering of light. The color is stable even at temperatures of 800°C. The FT-IR investigations have not detected the presence of inclusions capable of scattering light. The scanning electron microscopy has shown that there are significant amounts of Fe and Ti in the system, clearly concentrated as Ti/ Fe oxides hosted by the matrix, and potentially as light scattering nanometric inclusions. This type of inclusions would likely be syngenetic with the host quartz. The alternation between the blue and colorless areas could be the result of chemical fluctuations in the melt, which may have resulted in disruptions of the crystallization of the light scattering inclusions.
